At 4 kW (10.2 A rated, 20.4 A overload), the 6SL3520-0XA24-0AF0 marks the transition point in the FSB frame: below 4 kW, FSB relies on natural convection (134 mm depth); at 4 kW, a forced-air fan extends the depth to 169 mm. This is the drive you choose when a 3 kW G115D is thermally marginal but stepping up to FSC would oversize the installation footprint.

What changes at the 4 kW FSB thermal threshold?

The fan-cooled FSB at 4 kW delivers 172.9 W of power-loss dissipation with a 510–550 mA 24 V DC draw for the fan. The 175 Ω integrated braking resistor (10 W continuous) supports dynamic braking for inclined conveyor sections. If your application runs near full load continuously in a +40 °C ambient, the fan-cooled FSB is the correct choice — the convection-cooled FSB ratings assume intermittent duty or cooler ambient conditions. The 425 × 180 × 169 mm envelope shares the same mounting hole pattern (410 × 168 mm, 4× M5 bolts) as the smaller FSB and larger FSC frames.

Key specifications

The drive operates from a 3 AC 380–480 V supply (45–66 Hz) with an output frequency range of 0–550 Hz. High-overload capability delivers 200% for 3 seconds and 150% for 57 seconds. Integrated PROFINET and Ethernet IP interfaces connect directly to SIMATIC controllers. The built-in C2 RFI filter meets EN 61800-3 Category C2 conducted emission limits for industrial environments.